Sandia National Laboratories Building S9800B Halo Bunker/Firing Pit

Project Halo research included a series of experiments on a design for a high energy ruby laser.

Project Halo ran from 1961 through 1964 and included 11 tests. The first tests were conducted on open ground, the final two in the Halo Bunker/Firing Pit (Building S9800B). Those two test shots were completed in 1964. The firing pit was subsequently used on an ad hoc basis for explosive testing, primarily for flyer-plate studies. S9800B was demolished in 2002.

Building S9800B Halo Bunker/Firing Pit

In 1960, Theodore Maiman, a physicist at the Hughes Research Laboratory in Malibu, California, developed the first laser. The laser could produce short pulses of intense light and it sparked the imagination of the entire scientific community. Scientists dove into new programs to develop applications for the laser in a wide range of fields, including communication, weapons, health, and energy research.
Sandia was an early participant in laser studies. As early as 1960, for example, the lab's explosives development organization had a laser laboratory for testing ordnance. Investigations included determining which explosive compounds were sensitive to laser initiation. And, in 1961, Sandia initiated research to determine whether explosives could be used to boost a laser's energy.
Known as Project Halo, the research included a series of experiments on a design for a high energy ruby laser. A canister of Argon gas was surrounded by explosives and ignited remotely. The resulting implosion powered the ruby laser and produced a high-energy laser discharge.
Project Halo ran from 1961 through 1964 and included 11 tests. The first tests were conducted on open ground, the final two in the Halo Bunker/Firing Pit (Building S9800B). Those two test shots were completed in 1964. The firing pit was subsequently used on an ad hoc basis for explosive testing, primarily for flyer-plate studies. S9800B was demolished in 2002.

Overlooking Building S9800B from the north

Building S9800B

Building S9800B is a firing pit for explosives testing. It is a three-sided concrete structure with steel panels lining the interior of the firing pit. It is open on the north side. Earth-covered bunkers to house equipment extend from the firing pit on the west, south, and east sides.

The Historic Designation

Although associated with Sandia's early laser research, S9800B is of historic significance for its design, rather than the scientific tests that occurred there. It is significant because its design reflects the refinement of explosive testing into a more data dependent, innovative testing environment at Sandia.
In the early years of explosives research and development, explosive tests were conducted in open areas with scientists and equipment situated away from the blast or in a protective bunker. Results of the blast were evaluated after the event. At Sandia, as explosive testing matured, scientists developed a more controlled environment for explosive testing. Test sites more closely mirrored laboratories with a contained test area and data capture equipment located close to the blast site. From a protected environment, scientists and/or their equipment could capture details of an event while it was happening.
S9800B's design placed data capture equipment as close as possible to the test without being destroyed during the experiment. It is associated with Sandia’s established Cold War themes of weapon design, field testing, and environmental testing within its nuclear weapons mission.
In 2001, the Department of Energy/National Nuclear Security Administration/Sandia Field Office, in consultation with the New Mexico State Historic Preservation Officer, determined that S9800B was eligible for the National Register of Historic Places.

The Site

As early as 1950, Sandia was using land to the south of its main technical areas on Kirtland Air Force Base for explosives testing. The area was identified as the Coyote Test Field. It had been used during World War II for the proximity fuze testing program operated by Dr. E. J. Workman of the University of New Mexico. The Coyote Test Field eventually encompassed approximately 7,100 acres.
In 1954, Sandia's Plant Engineering organization completed Building 9800, a small concrete bunker for explosives test preparation and data recovery. The building and the related opened piece of ground to the southeast were used by Sandia's explosive test programs for a variety of different tests over the years.
The first Halo tests were conducted at a secluded site in the mountains near Coyote Canyon. However, the environment proved too rugged for the data catpure equipment and the tests were moved closer to Building 9800. Tests were conducted in the open air surrounded by an earth embankment. This location was used for most of the Halo experiments and it is where the new firing pit, identified as Building S9800B was built.

Looking northeast at the front (west side) with entrance

Building 9800

Building 9800, the bunker at the Project Halo site before the S9800B (the firing pit) was built.

East and north sides of Building 9801

Building 9801

Building 9801 served as an equipment and personnel shelter at the 9800 firing site.

The Firing Pit

Sandia's Plant Engineering organization designed and built S9800B. The structure is an open-air three-sided firing pit surrounded on its west, south, and east sides by metal earth-covered instrumentation bunkers identified as Bunkers 1, 2, and 3, respectively.
The firing pit is concrete, its interior lined with layers of plywood topped with steel panels and attached to three concrete walls with anchor bolts. Each side of the firing pit has a porthole with an observation tube extending back through the concrete wall to an expansion chamber. The expansion chamber then connects through a 1' 6" concrete wall into the instrumentation bunker, allowing data to be captured and relayed to recording systems inside.
The only alteration to the building from its original design was the replacement of the sandbags that served as retaining walls at the outside (north) edge of the east and west sides of the firing pit. In 1964, shortly after the structure's completion, these were replaced with Armco metal retaining walls.

Details

Soon after its original construction, the firing pit received new retaining walls to hold back the earth berm on the east and west sides of the open north end of the pit.

Armco retaining walls on east edge of teh firing pit's north side

Walls Damaged by Explosives

Retaining walls hold back the earth berm covering the bunker that extends from the east side of the firing pit. The retaining walls and the concrete edge of the firing pit display damage from explosives testing.
The Armco metal retaining walls were produced and sold by Armco Steel Corporation, formerly The American Rolling Mill Company. In 1978, Armco Steel Corporation became Armco Inc. In 1999, Armco Inc. merged with AK Steel Corporation. Armco produced rolled steel products used widely in American industry. The company's products are ubiquitous in road barriers, culverts, and a multitude of different types of pre-fabricated, pre-painted steel panel buildings. Armco products are found throughout the military and nuclear weapons complex test facilities built in the second half of the 20th century.

Firing Pit

The Firing Pit is a 3-sided concrete structure that forms an inverted trapezoid 30' wide at the top tapering to 10' wide at the bottom. The floor of the center of the structure is a square blast pad measuring 9' 1" on each side. The three side walls and the bottom of the firing pit are covered with layers of plywood and a ½" steel firing pit liner anchor bolted in place.
Each of the three side walls has a porthole extending via an observation tube through the wall to the expansion chamber behind it. The open north side of the pit has a concrete apron extending out to the north edges of the east and west sides. There is a steel and concrete opening through the apron on the west side of the apron. This is identified as the Firing Unit Well and allowed access to cables for equipment set-up.
The bunkers are surrounded by and covered in an earth berm rising 11' 2" to the top edge of the firing pit. It is held in place along the north edge by Armco metal retaining walls. On the west, south, and east sides it slopes down to the front edge of each bunker entrance, held in place by 1' thick concrete wall extending 17' from the bunker's outer wall.

North side of the firing pit

North Side of the Firing Pit

The firing pit site was cleared and leveled with the earth berm that covers its bunkers rising around it to the south. The site became overgrown when the firing pit was no longer used and teh structure blended into the landscape. The firing pit in the center is open on the north side between the retaining walls that hold back the earth berm.

Northeast corner of the firing pit

Reinforced Concrete Corner

The firing pit wall is reinforced concrete poured to angle down to meet the pit floor. The inner pit wall is covered in three layers of 1/4" plywood topped with ½" steel liner plates attached to the concrete with metal anchor bolts.

East Side of Firing Pit

The Armco retaining wall on the outer edge of the east side of the firing pit reflects damage from multiple tests and signs of disuse. A concrete test block rests against the wall and the native vegetation is breaking through the pit's floor and joints.

Northwest Corner of Firing Pit

The intersection of teh west side of the firing pit and teh metal retaining wall shows multiple pits and holes from explosives testing.

Three-sided firing pit with steel plate lining the sides and bottom

Inside the Firing Pit

The interior of the firing pit is lined with steel panels over plywood bolted to reinforced concrete. The bottom panel of the pit became detached over time.

Firing Unit Well

The firing unit well sits in the ground just north of the bottom of the firing pit. The well provides cable access and storage—it is a metal-framed box with steel panels forming a cover. In later years it was also covered with a wood panel, visible on the left.

Firing unit well with all but one of the steel plates covering it removed to show its construction

Inside the Firing Unit Well

The firing unit well is a metal-framed box with steel lining extending approximately 1' with concrete walls below that. Cables entered the box via opening on the right (west) side.

Bunker 1 (West Bunker)

Bunker 1 is a one-story structure extending from the west side of the firing pit. It is 14' wide x 24' long. The east and west end walls are 1' 6" thick. The expansion chamber extending from the porthole in the west side of the firing chamber to the east wall of the bunker is 7'6" long x 8' wide.
The building's earth berm forms a flat graded top that extends over all three bunkers and slopes down the sides of each.
The entrance to Bunker 1 is on its west end and is reached by walking through a concrete-walled corridor 6' wide x 17' long. The exterior concrete walls of the corridor are 1'' thick and slope down from top of the berm to ground level.

View from top of Bunker 3 on east side

West Side of Firing Pit (Bunker 1)

Bunker 1 extends from the west side of the firing pit.

Porthole Into Bunker 1

The porthole on the west side of the firing pit looks into Bunker 1.

Bunker 1 interior; view from west

Bunker 1 Interior

Bunker 1 is formed from a curved steel arch that rests on a concrete berm. The bunker has a poured concrete floor. A steel-reinforced rectangular opening in the center of the east wall provides a view through an expansion chamber to the porthole in the west side of the firing pit.

Bunker 1 Interior Detail

The east wall of Bunker 1 features a rectangular steel-reinforced opening to the porthole to the firing pit. there is a metal-caged light fixture above the porthole.

Bunker 1 Signal Rack

Some equipment remained in S9800B until it was demolished. A signal rack mounted on the north side of Bunker 1's interior remained in place.

Bunker 1 Entrance

The entrance to Bunker 1 is a metal pedestrian door on the east end.

Bunker 2 (South Bunker)

Bunker 2 is a one-story structure extending from the south side of the firing pit. It is 14' wide x 12' long. The north wall is 1' 6" thick concrete and the south wall is 1' 5" concrete.
An expansion chamber 7' 6" long x 8' wide extends from the exterior of the bunker's north wall to the back wall of firing pit. The bunker's entrance is on south end and is reached by walking through a concrete-walled corridor 6' wide x 17' long. The exterior concrete walls of the corridor are 1' thick and slope down from top of berm to ground level.

South Side of Firing Pit

The south side of the firing pit backs onto the north end of Bunker 2.

Porthole into Bunker 2

The porthole in the south side of th efiring pit leads into Bunker 2. The steel plate covering the firing pit's interior shows damage from testing. Remains of the gutta percha used to attach covers to the porthole are visible around edge of the steel plate surrounding the outer edge of the porthole.

South Side of S9800B

Wood stairs lead to the top of S9800B. The concrete entrance to Bunker 2 (the south bunker) is also on the structure's south side.

Stairs at S9800B

Stairs on exterior of south side of S9800B provided access to the top of the structure.

Stairs Detail

The disused stairs fell into disrepair once testing ended at the site.

View of Bunker 2 from the northwest

Bunker 2 Interior

As in Bunkers 1 and 3, curved metal panels form Bunker 2's ceiling and walls, connecting to the concrete berm near the floor on the east and west sides. Equipment stands and empty shelving stand on the poured concrete floor.

Bunker 2 interior; view from southeast

Bunker 2 Details

The signal rack on the north end of the west wall of Bunker 2 remains intact. The rectangular steel-reinforced opening in the north wall leads to a porthole in the south wall of the firing pit. The light fixtures on the walls above the signal rack and the north wall opening enclose the light bulbs in metal cages.

Bunker 3 (East Bunker)

Bunker 3 is a one-story structure extending from the east side of the firing pit. It is 14' wide x 14' long with a 1' 5" thick concrete wall on the west and a 1' 6" concrete wall on the east end.
A 7' 6" long x 8' wide expansion chamber extends from the exterior west wall to the back wall of firing pit. The bunker entrance is on the east end and is reached by walking through a concrete-walled corridor 6' wide x 17' long. The exterior concrete walls of the corridor are 1' thick and slope down from top of berm to ground level..

East Side of Firing Pit

The east side of the firing pit meets the west end of Bunker 3 (the east bunker). The porthole opening extends into Bunker 3 on the east side of the structure, providing line-of-site for equipment in the bunker.

View from exterior of porthole on east side of firing pit

Porthole on East Side of Firing Pit

The east side porthole opens to the expansion chamber extending to the west wall of Bunker 3. The steel plate surrounding the porthole on the wall of the firing pit is broken and damaged from testing and age. The nuts on the anchor bolts holding the steel plate to the wall of the firing pit are visible.

Bunker 3 Entry

Concrete retaining walls form the entryway to the bunker, which has a metal pedestrian door. A metal safety railing is visible above the bunker entrance and the Armco retaining wall on the east side of the firing pit is visible on the far right. The earth berm covering the bunkers is covered in native vegetation.

Bunker 3 Entry Detail

1' thick concrete retaining walls form the sides of the entryway to Bunker 3. The pedestrian door into the bunker is metal.

Bunker 3 Interior

Curved corrugated metal panels form the ceiling and wall reaching to the concrete berm along the north and south edges of the room. The floor is a poured concrete slab. The room is painted matte black. The interior of the west wall is a steel panel. In the center of the west wall, the rectangular steel-reinforced opening provides a view through the expansion chamber extending to the porthole in the firing pit. A signal rack stands on the left (south) wall to the left of the expansion chamber opening. There are metal-cage light fixtures above the port and on the side walls.

Bunker 3 Fixtures

There are metal-cage light fixtures and a metal pedestrian door opening to the exterior. The room is painted matte black to absorb light.

The Tests

In the last two Halo tests, the ruby laser was placed in the center of a cylinder lined with high explosives. The laser was triggered at 48 points located uniformly around the circumference of the canister.
Bunker 1 housed a liquid calorimeter capable of detecting energy as small as 20 joules. The calorimeter captured the ruby beam through a system of lenses.
Bunker 2 housed two cameras. An Avco streak camera observed the laser output and the advance of the luminous front. An Electro-Optical Instruments (EOI) framing camera observed the output of the ruby on a screen. The cameras captured about 20% of the ruby output exiting a slit in the cylinder by means of a plain glass beam splitter.
Bunker 3 housed two TRG calorimeters, an FW114 photo diode, and a time resolved spectrograph. Two plain glass reflectors and a lens captured beam energy and recorded it.

Bunker Arrangement

Arrangement of bunkers around firing pit and instrumentation layout from the 1964 tests.

Post-Halo S9800B

After the Halo test series ended in 1964, the S9800B bunker was not assigned to a specific project or group. Instead, it functioned as a generic explosive test site that could be used by any group that needed the capabilities or configuration that the site provided. The Firing Pit could handle an explosion of approximately 50 pounds of explosives and provide data capture for the event. The site was frequently used for flyer-plate studies. Typically, an explosive charge was used to accelerate a plate made of steel, aluminum, or copper towards a target. Other testing included shrapnel studies, blast force tests, and penetrator studies. S9800B ceased to be used for any type of testing in the 1990s.

Demolition

In late 2002 and into 2003, S9800B was demolished and the site restored. The Facilities crew allowed the photographer to obtain a few shots of the demolition activity, which revealed the structure's underlying construction.
In this view from the northwest, the steel plates lining the firing the firing pit have been removed and the pit collapsed into rubble (center of photograph; north edge of structure). The earth berms have been removed from the bunker revealing their underlying constructing. Bunker 1 (the west bunker) is visible in the right foreground—note the concrete walls at the front and back of the bunker, as well as the corrugated metal room construction. Bunker 2 (south bunker) is visible to the right and behind Bunker 1.

Bunker 2 and 3

Bunker 2 (south bunker) on the left and Bunker 3 (east bunker) on the right. The concrete entryways and walls at the front and back of each bunker are clearly visible, as is the east wall of the firing pit.